1Field of the Invention
The present invention relates to a signal processing circuit for a record/reproducing apparatus employing an optical recording medium (including magneto optical recording medium), and more particularly to a signal processing circuit adapted for use in an add-on optical record/reproducing apparatus, an overwritable magnetooptical record/reproducing apparatus or an overwritable phase-change optical record/reproducing apparatus (hereinafter collectively called 2-beam optical record/reproducing apparatus), or an erasable magnetooptical record/reproducing apparatus or an erasable phase-change optical record/reproducing apparatus (hereinafter collectively called 3-beam optical record/reproducing apparatus).
2. Related Background Art
In a magnetooptical record/reproducing apparatus for information recording and replay with a magnetooptical recording medium such as a magnetooptical disk or card, the information recording is usually accomplished by three modes, namely erasure (E), recording or writing (W), and replay or reading (R).
For example, as shown in FIG. 6, in order to effect these three modes of erasure, writing and reading on a magnetooptical disk at a high speed, a controller 6, for controlling the functions of the magnetooptical disk record/reproducing apparatus under the commands of a host computer 7 has conventionally been equipped with an erasure (E) signal process circuit 62, a write (W) signal process circuit 63 and a read (R) signal process circuit 64, respectively corresponding to signals of an erasure head 2, a write head 3 and a read head 4.
FIG. 6 shows a conventional example of signal processing in a 3-beam magnetooptical disk drive, of which functions will be explained in the following.
At first an old signal already recorded on a magnetooptical disk (hereinafter simply called disk) 1 is read by the erasure (E) head 2, and the signal 2a from the erasure head is binary digitized by a replay process circuit 22 for the erasure head. The digitized signal is supplied, as the read data 22a, through an interface 5 to an erasure signal process circuit 62 in the controller 6. For erasing the old signal, the process circuit 62 releases an erasure gate signal 22b through the interface 5. An erasure laser drive unit 21 generates an erasure signal 21a in synchronization with erasure gate signal 22b, thereby erasing the signal recorded on the disk 1 by the erasure head 2.
Then, for recording a new signal in the erased portion, a signal 33a read by the write head 3 is binary digitized by a replay process circuit 32 of the write head, and supplied, as the read data 32a of the write head, through the interface 5 to a write signal process circuit 63 of the controller 6. In response, process circuit 63 releases, through the interface 5, a write gate signal 20a and write data 30a. A write laser drive unit 31 generates a recording signal 31a, in synchronization with the write gate signal 20a, thereby writing a new signal in the erased portion of the disk 1.
Then, in response to a read gate signal 40a supplied from a read signal process circuit 64 of the controller 6 through the interface 5, a reading laser drive unit 41 activates a reading head 4, thereby reading the new signal 4a written on the disk 1. The signal 4a is binary digitized by a replay process circuit 42 for reading, and supplied, as the read data 42a of the reading head, through the interface 5 to the controller 6 receiving commands from the host computer 7.
In order to accomplish erasure, recording and reproduction at a high speed, namely without waiting time for disk rotation, there has been required the controller 6 of a complex structure as explained above.
In the foregoing there has been explained a case of utilizing a disk as the recording medium, but the situation is the same when a card is employed as the recording medium.
As explained in the foregoing, in the case of writing a new signal in an already recorded area with a conventional magnetooptical record/reproducing apparatus, it is necessary to erase the already recorded signal with the erasing beam and to write the new signal by the writing beam, and the controller is inevitably complex as three signal processing circuits for erasure, writing and reading are required in the controller.
Also in an optical record/reproducing apparatus employing an optical recording medium such as a disk-shaped or card-shaped medium, there is often required a read-after-write (RAW) check in which the newly recorded signal is immediately replayed for confirming correct recording. This check is accomplished by writing a new signal with a recording beam, and replaying the new signal recorded on the optical recording medium with a reproducing beam, and these operations are controlled by the controller and the host computer.
In order to accomplish the signal processing for such RAW check at a high speed, the signal processing for recording and replay has to be conducted without waiting time for rotation in case of a disk-shaped medium, or without waiting time for re-scanning in case of a card-shaped medium, and the signals reproduced from the beams are sent to the controller for signal processing.
In the following there will be explained, with reference to FIG. 6, the operations of RAW check in a conventional disk-shaped optical recording medium (hereinafter called optical disk). The high-speed recording and replay to or from the optical disk have conventionally been conducted by the commands from the host computer 7. The controller 6, for controlling the functions of the optical disk record/reproducing apparatus according to such commands is provided with a recording signal process circuit 63 and a replaying signal process circuit 64, respectively corresponding to the signal from the recording head 3 and the signal from the reproducing head 4.
For recording a new signal in an area of the optical disk 1, signal replaying is conducted at first by the recording head 3, in order to detect an area available for signal writing. The signal 33a read by a recording optical unit 33 of the recording head 3 is binary digitized by a replay process circuit 32 for recording, and is supplied, as the reproduced data 32a of the recording beam, through the interface 5 to the recording signal process circuit 63 of the controller 6. After confirmation that the area is available for signal writing, the controller 6 sends a recording command to the recording signal process circuit 63, which, in response, sends a recording gate signal 20a and recording data 30a through the interface 5 to the recording head 3. A recording laser drive unit 31 of the recording head 3 releases a recording signal 31a in synchronization with the recording gate signal 20a, thereby causing the recording optical unit 33 to write the signal onto the optical disk 1.
Then, in response to a command from the host computer 7, the reproducing signal process circuit 64 of the controller 6 activates the reproducing head 4 through the interface 5, thereby reading the signal recorded on the optical disk 1. In the reproducing head 4, the replay signal 43a from the reproducing optical unit 43 is binary digitized by the replay process circuit 42, and supplied, as a replay signal of the reproducing beam, through the interface 5 to the controller 6.
The RAW check is accomplished in this manner.
In such conventional optical record/reproducing apparatus, the RAW check has been conducted by recording a signal with the recording head 3, replaying the new signal, recorded on the optical disk 1, with the reproducing head 4, and checking the reproduced data 42a of the reproducing beam by the controller 6.
In order to achieve RAW check at high speed, or, without waiting time for disk rotation, there are required the reproduced data 32a of the recording beam and the reproduced data 42a of the reproducing beam. Consequently the 2-beam optical record/reproducing apparatus requires two signal process circuits 63, 64, and the 3-beam apparatus requires three signal process circuits. Also the speed of the operations is still limited by the judgement of the controller 6.